Treating diseases by using the interventional method through catheter technology is a therapy applied more and more widely at present. Various materials, devices and medicines are placed into heart and arteriovenous vessels of a human body by the catheter-based interventional therapy.
For example, an occluder (such as, atrial septal defect (ASD) occluder, ventricular septal defect (VSD) occluder, patent ductus arteriosus (PDA) occluder, patent foramen ovale (PFO) occluder, etc.) is placed to a defective part of the heart by the catheter-based interventional method to occlude the defect so as to treat the congenital heart disease. As a well-known device, with the threaded connection between the device and a pusher, the device is conveyed to a predetermined part by the pusher, and then the device and the pusher are disengaged by releasing the threaded connection. For such a device, the threaded connection may realize the reliable and safe connection between the device and the pusher, and may also achieve controllable release. In other words, if the size of the device is improper, or when the device cannot expand well, the device may be accommodated into a delivery catheter again and then replaced with a new device appropriate for repositioning and realizable release.
For another example, an occluder is placed into the left atrial appendage by the catheter-based interventional method in order to prevent thrombus caused by left atrial appendage due to atrial fibrillation that could transfer up to the brain so as to result in stroke, or to prevent the thrombus from reaching other parts of the body through the human blood circulatory system and then resulting in systemic embolism. The occluder is placed into the left atrial appendage in order to occlude the left atrial appendage and block the blood flow entering the left atrial appendage, so that this may eliminate the risk of thrombus caused by the left atrial appendage due to atrial fibrillation and avoid apoplexia. At present, the device is generally connected with an introducer by threads. All the devices may be classified into two categories roughly by their structures: a plug type left atrial appendage occluder shown in FIG. 1 and FIG. 2, and a plug-and-disc type left atrial appendage occluder shown in FIG. 3. In FIGS. 1-3, 1 refers to left atrium (LA); 2 refers to left atrial appendage (LAA); 3 refers to the wall of left atrial appendage cavity; 4 refers to a flow blocking membrane of the plug type left atrial appendage occluder; 5 refers to a main body of the plug type left atrial appendage occluder; 6 refers to a pit-shaped gap between the plug type left atrial appendage occluder and the left atrial appendage; 7 refers to a main body of the plug-and-disc type left atrial appendage occluder; and, 8 refers to a flow blocking membrane of the plug-and-disc type left atrial appendage occluder. The plug type left atrial appendage occluder is made into a spherical, cylindrical or conical plug with a flow blocking membrane. The plug is elastic and may deform in the left atrial appendage to fit with the shape of the left atrial appendage cavity for the purpose of plugging the left atrial appendage, while the flow blocking membrane on the plug may block off the blood flow. The plug-and-disc type left atrial appendage occluder is a complex of a cylindrical plug and a disc-shaped part, and a flow blocking membrane is also sutured onto the disc. The cylindrical plug is placed into the left atrial appendage cavity to fix the whole device. The disc-shaped part covers the entrance of the left atrial appendage and is used for blocking off the blood flow entering the left atrial appendage.
When these devices are placed into the heart, arteriovenous vessels and the left atrial appendage of a human body by the catheter-based interventional method, because the heart and arteriovenous vessels of the human body, and particularly the anatomical structure of the left atrial appendage, are complicated, it is required that a device must reach a predetermined position exactly and fit well with the anatomical structure of the predetermined position, mechanical requirements and dynamic requirements of the blood flow. Therefore, the structure of the device must be designed very precisely. Under the premise of causing minimal damage to the human body, the skin close to a vessel is punctured first, and then a guide wire enters the vessel from the punctured pore. Under the guidance of the guide wire, one end of a catheter reaches the predetermined position, while the other end thereof remains outside of the body. Then, the device is delivered to the predetermined position by the catheter and a pusher. During such an operation, a very small and flexible catheter is required, and the catheter and the guide wire are designed to have good development under the X-ray. Once the catheter reaches the predetermined position, the guide wire is removed, and then the device is guided to the tail end of the catheter by the pusher through a channel built by the catheter. When the device is totally exposed from the tail end of the catheter, the device is detached from the pusher to realize the release of the device.
At present, there are many limitations for the left atrial appendage occluder.
1. The following shows the limitations of the plug type left atrial appendage occluder.
(a) When the device is plugged into the left atrial appendage, the deformability of this device is limited, and the shape of the entrance of the left atrial appendage is very irregular. Therefore, many small pit-shaped gaps 6 are formed between the part attached with membrane and the outer edge of the entrance of the left atrial appendage (as shown in FIG. 2), equivalent to many artificial left atrial appendages formed. Because the entrance of the left atrial appendage cannot be blocked completely, it is difficult to eliminate the thrombus caused by the left atrial appendage due to atrial fibrillation, so that the thrombus endogenus of the “artificial left atrial appendage” device will increase the probability of forming left atrial appendage thrombus.
(b) The anatomical structures of left atrial appendages of all people are in different shapes, such as an oval shape, a peanut shape, etc., and some left atrial appendages have multiple cavities, so the plug type left atrial appendage occluder cannot fit anatomical structures of all left atrial appendages completely and cannot be stably fixed.
(c) The depths of left atrial appendages of all people are different, so the length of the plug type left atrial appendage occluder cannot fit various depths of left atrial appendages.
2. The following shows the limitations of the plug-and-disc type left atrial appendage occluder.
(a) The plug-and-disc type left atrial appendage occluder has a complex body, in which the plug part and the disc part cannot be deformed completely and independently. When the plug is plugged into the left atrial appendage, the shape of the plug needs to comply with the internal structure of the left atrial appendage, so that the disc part will encounter the traction of the plug part when buckled on the entrance of the left atrial appendage. As a result, the disc part cannot fit fully with the entrance of the left atrial appendage. Therefore, the blood flow cannot be blocked completely, and it is difficult to achieve the best occlusion effect.
(b) Because the anatomical structures of left atrial appendages of all people are in different shapes, it is required to find an optimal fixing point in the cavity of the left atrial appendages. Therefore, it is required that the plug part may realize the best fixation in different depths. However, because the lengths of the plug part and the disc part are limited for adjustment, it is difficult for most left atrial appendages to achieve the best fixation and blockage of blood flow.
3. Furthermore, most of left atrial appendage occluders plugged in the left atrial appendage is of a closed structure, so the left atrial appendage occluders are difficult to fit different shapes of cavities of left atrial appendages.
4. In addition, it is required to add an anchor structure on an occluder to fix the left atrial appendage occluder. However, the anchor structures of present products are unreasonable; for example, the anchors of some left atrial appendage occluders are several fine wires equipped on the occluders by suture lines. It is difficult for such an anchor to penetrate through the wall of the left atrial appendage under the condition of compression in the cavity of the left atrial appendage, so that the stable fixation cannot be realized. Besides, the anchors of some left atrial appendage occluders have enough puncture force but pose an obstacle to the withdrawal of an occluder, so that the occluders cannot realize the repeated positioning.